Filter devices of this type represent the prior art. For example, WO 2009/109212 A1 discloses a device of this kind in the form of a return line filter mountable in a fluid storage tank. Such in-tank filter devices are preferably used in working devices provided with a hydraulic system, such as excavators, wheel loaders or telehoist load luggers etc., which are provided with a working hydraulic system, for example in the form of hydraulic cylinders that can be controlled and supplied by pumps. During operation, as known per se from the aforementioned document, fluid passes through the filter element from the inside forming the unfiltered side toward the outside of the filter medium forming the clean side. The cleaned fluid reaches the tank content through fluid passages in the filter housing immersed in the tank. To facilitate the replacement of a used filter element, the retaining body positioning the corresponding filter element in its operative position is connected with a removable lid and, together with it, removable from the housing during a replacement process.